You can use the LargeImageSource or SmallImageSource properties to add large or small images to your C1ToolbarButtons.

Using the Designer

1.  Right-click the C1ToolbarButton control on your page and select Properties.
2.  Locate the LargelImageSource property and click the ellipsis button next to it. The Choose Image dialog box appears.
3. Click the Add button and select the image you wish to add to it and click OK.